Optical circuit devices are made workable generally by connecting a number of optical components via optical fibers. To operate an optical amplifier, for example, thirty or more optical fibers are joined to one another to connect optical components. There are some known techniques for joining optical fibers. One method is using optical fiber cable with a connector, which connector is to be connected to a counterpart connector via an optical adaptor. Another method is splicing optical fibers. To join a number of optical fibers all together, the latter method is generally employed because it is advantageous from the viewpoints of durability against loss of optical signals and stowing efficiency. In general, the more the optical fibers to be connected, the greater the signal loss and the required stowing space.
FIG. 1A through FIG. 1E illustrate a conventional method for splicing optical fibers using a fiber fusion splicer. In FIG. 1A, optical fibers 102-1 and 102-2, which are used to connect optical components inside an optical circuit device 101, are pulled out from an opening 101a of the optical circuit device 101 such that the optical fibers 102-1 and 102-2 can be placed on a splicer (not shown). Then, in FIG. 1B, the ends of the optical fibers 102-1 and 102-2 are spliced by the splicer. The spliced part is reinforced by a protection sleeve 104. By this splicing process, optical components (not shown) arranged in the optical circuit device 101 are connected to each other via the optical fibers 102-1 and 102-2. The spliced optical fibers 102-1 and 102-2 involve a surplus length produced for the purpose of fiber fusion splicing using the splicer. The surplus length of the spliced optical fibers 102 is stowed in the optical circuit device 101. This process is called a “surplus length stowing process”.
As illustrated in FIG. 1C, the looped optical fibers 102-1 and 102-2 (which are collectively referred to as “optical fibers 102”) are twisted in figure eight (8). Then, the twisted optical fibers 102 are folded onto the optical circuit device 101 as illustrated in FIG. 1D, and further folded at the twisted portion as illustrated in FIG. 1E such that the entirety of the surplus length of joined optical fibers is accommodated in the case of the optical circuit device 101.
The acceptable bend radius of the optical fibers 102 is confined to prevent degradation of optical signals propagating through the optical fibers 102. Microbending deformation due to twisting of optical fibers will cause degradation of optical signals. Since it is difficult to visually determine at which point microbending exists, it is hard to specify and repair the portion at which optical signal loss has occurred due to the microbending. Accordingly, it is preferred not to twist the optical fibers during the surplus length stowing process.
Although in FIG. 1A through 1E each of the optical fibers 102-1 and 102-2 pulled out from the opening 101a is depicted in a single line for the purpose of simplification, a set of optical fibers (e.g., ten optical fibers) are pulled out from each side of the opening 101a of the optical circuit device 101 in the actual process. A set of optical fibers are arranged in parallel and joined end-to-end to the counterpart set of optical fibers by fusion splicing. The collectively spliced optical fibers are twisted or folded during the surplus length stowing process, and each one of the optical fibers has to be treated very carefully. Accordingly, the stowing work becomes complicated with increased workload. In addition, if the surplus length stowing process is carried out by hand, the handiwork varies depending on the workers.
A known technique for stowing the surplus length of optical fibers is bundling the surplus lengths and tucking the bundle between surplus length stowing sheets. (See, for example, Japanese Laid-Open Patent Publication No. 61-116302). Another known method is winding the surplus lengths of optical fibers and fixing the winding in an annular groove. (See, for example, Japanese Laid-Open Patent Publication No. 2003-156634).
In view of these problems, there is a demand for an optical fiber holder that can hold a set of optical fibers in good order without twisting, while satisfying the allowable (minimum) bend radius. There are also demands for an optical device using the optical fiber holder and a surplus length stowing method for optical fibers.